There is a major need for producible long-wave-infrared (LWIR) detector arrays in the range of 8 to 18 .mu.m that operate at temperatures of 65K or higher, where space-qualifiable refrigerators are being developed. Considerable effort has been expended to develop II-VI compounds such as HgCdTe to achieve such high performance arrays; however, serious material problems have limited their development into LWIR arrays.
Other established approaches, such as silicon impurity band detector arrays, require cryogenic cooling below 12K. Recently, B. F. Levine et al in Applied Physics Letters, Vol. 53, p. 296-298 (1988) have reported the growth of single pixel quantum well detectors of AlGaAs/GaAs by molecular beam epitaxy (MBE); such detectors have demonstrated good detectivity at 8 .mu.m wavelength (and more recently at longer wavelengths), but require incident radiation to be deflected into the plane of the semiconductor wafer, which complicates their development into focal plane arrays (FPA).
There continues to be a pressing need for LWIR detectors with high detectivity performance at high operating temperatures (&gt;65K) which can be produced into large reliable arrays compatible with silicon or GaAs multiplexer/-readout technology for FPAs.